Retrieving correct domain when Netbios and FQDN values are different

Question

I am trying to retrieve the current domain object of the user. I am running into issues when the FQDN domain name is different than the Pre-Windows 2000 domain name (netbios).

String domainName = "????";    
Domain d = Domain.GetDomain(new DirectoryContext(DirectoryContextType.Domain, domainName)));

Exception thrown:

System.DirectoryServices.ActiveDirectory.ActiveDirectoryObjectNotFoundException: The specified domain does not exist or cannot be contacted.

I'm having trouble figuring out which domain name I should use to retrieve the current user Domain. My current implementation is using the FQDN string but that seems to be failing when the netbios is changed.

Any pointers to lead me in the correct direction? Thanks!